Top 98 Node.js Interview Questions & Answers (2026)

01 What is Node.js? 02 What is the V8 engine? 03 What is the difference between Node.js and the browser JavaScript environment? 04 What is npm? 05 What is package.json? 06 What is the event loop in Node.js? 07 What is non-blocking I/O? 08 What are callbacks in Node.js? 09 What is callback hell and how do you avoid it? 10 What are Promises in Node.js? 11 What is async/await in Node.js? 12 What is the require() function in Node.js? 13 What is module.exports in Node.js? 14 What is the fs module in Node.js? 15 What is the http module in Node.js? 16 What is Express.js? 17 What is middleware in Express.js? 18 What is the path module in Node.js? 19 What is __dirname and __filename in Node.js? 20 What is the os module in Node.js? 21 What is process in Node.js? 22 What is the events module and EventEmitter in Node.js? 23 What is the difference between synchronous and asynchronous code in Node.js? 24 What is the buffer in Node.js? 25 What are streams in Node.js? 26 What is npm install and what does it do? 27 What is package-lock.json? 28 What is the difference between dependencies and devDependencies? 29 What is nodemon? 30 What is the dotenv package and how is it used? 31 What is REST API and how do you build one with Node.js? 32 What is JSON.parse() and JSON.stringify() in Node.js? 33 What is CORS and how do you enable it in Node.js? 34 How do you handle errors in Express.js? 35 What is the query string in a URL and how do you access it in Express? 36 What is the util module in Node.js? 37 What is the crypto module in Node.js? 38 What is the child_process module in Node.js? 39 What is the difference between setTimeout and setImmediate in Node.js? 40 What is process.nextTick() in Node.js? 41 What is the cluster module in Node.js?

01 What is the event-driven architecture in Node.js? 02 What is middleware chaining in Express.js? 03 What are Worker Threads in Node.js? 04 What is libuv in Node.js? 05 What is the difference between cluster and Worker Threads? 06 What is backpressure in Node.js streams? 07 What is the difference between readFile and createReadStream? 08 What is JWT and how is it used in Node.js? 09 What is bcrypt and why is it used for passwords? 10 What is Mongoose and how does it relate to MongoDB? 11 What is connection pooling in Node.js database access? 12 What is rate limiting and how do you implement it in Node.js? 13 What is input validation and sanitization in Node.js? 14 What is the difference between authentication and authorization? 15 What is session management in Node.js? 16 What is Passport.js? 17 What is the difference between SQL and NoSQL databases and when to use each with Node.js? 18 What is Redis and how is it used in Node.js applications? 19 What is GraphQL and how does it differ from REST in Node.js? 20 What is WebSocket and how do you implement it in Node.js? 21 What is the difference between monolithic and microservices architecture in Node.js? 22 What is a message queue and why is it used in Node.js applications? 23 What is Prisma and how is it used in Node.js? 24 What is the Sequelize ORM in Node.js? 25 What is TypeORM in Node.js? 26 How do you implement logging in a Node.js application? 27 What is PM2 and why is it used in production? 28 What is Helmet.js and why should you use it? 29 What is dependency injection in Node.js? 30 How do you write unit tests for Node.js applications? 31 What is the difference between PUT and PATCH in REST APIs? 32 What is HTTP status codes and which ones are most important in Node.js APIs? 33 What is environment-based configuration in Node.js?

01 How does Node.js handle concurrency without multiple threads? 02 What is the Node.js memory model and how does garbage collection work? 03 What are memory leaks in Node.js and how do you detect them? 04 What is the difference between process.exit() and throwing an uncaught exception? 05 What is the N+1 query problem and how do you solve it in Node.js? 06 What is circuit breaking pattern in Node.js microservices? 07 What is graceful shutdown in Node.js and how do you implement it? 08 What is connection pooling for HTTP requests in Node.js? 09 What are common Node.js security vulnerabilities and how do you prevent them? 10 What is the difference between horizontal and vertical scaling in Node.js? 11 What is Node.js streams backpressure and how does pipe() handle it? 12 What is the Twelve-Factor App methodology as it applies to Node.js? 13 What is serverless computing and how does Node.js fit in? 14 What is the Observer pattern and how does it relate to Node.js EventEmitter? 15 How do you optimize a slow Node.js API endpoint? 16 What is NestJS and how does it differ from Express? 17 What is async context tracking in Node.js? 18 What is OpenTelemetry and how is it used in Node.js? 19 What is the Module Federation and how does it apply to Node.js? 20 How does HTTPS work and how do you set up TLS in Node.js? 21 What is HTTP/2 and does Node.js support it? 22 What is the difference between Fastify and Express? 23 What is a Proxy in Node.js and how is it used? 24 What is Domain-Driven Design (DDD) and how is it applied in Node.js?